There is a very large number of patents in the field of human powered vehicles and exercise equipment, and a large percentage of the more recent ones utilize one-way clutches and levers, as does the present invention. The following discussion will emphasize that portion of the patent art.
Friction and other losses are important in human powered vehicles, as they reduce the amount of power which is expended and which is not applied to propelling a vehicle. These losses could be categorized as friction losses, rewind spring losses, and dynamic losses due to constant acceleration and deceleration of the reciprocating components of the one-way clutches and associated chains, pulleys, etc.
Friction losses by rotating shafts, chains operating on sprockets, etc, are not a big problem as long as the mechanism is not complicated and has few moving components.
The energy loss associated with the rewind spring in most cases is not very significant because in reality the only energy that is lost is friction in those associated parts, because in most designs any excess energy deposited in the spring during the power stroke is returned to the system during the following rewind stroke.
The dynamic losses due to the constant start, stop, and reverse movement of the reciprocating components of the one-way clutches and their associated members, however, are considerable. In many designs which have several clutches, and often have long chains and/or heavy springs attached, it is possible that the design is inefficient enough that it is not useful.
This situation, in many cases, confines the system to a low speed operation, because these dynamic power losses increase as the square of the speed of the reversals. The simplicity of a design and the length of its power stroke are, therefore, very important in respect to its effectiveness. The weight of the reciprocating components is also important; a lighter weight reduces the dynamic losses due to reversals. The most efficient system will have few and lightweight parts.
Designs which are obviously inefficient might include U.S. Pat. No. 5,272,928, to Young, U.S. Pat. No. 5,690,346, to Keskitalo, and U.S. Pat. No. 6,554,309, to Thir, all of which have at least four one-way clutches with associated chains, sprockets, drums, etc.
Many of the prior art designs, possibly including the three above, are so complicated and expensive to manufacture that they may not be feasible, and their upkeep might also be prohibitive. The weight, and also the appearance, of many of these more complicated designs could also become a factor.
Those designs which use a spring to rewind a one-way clutch often show us a spring which does not allow nearly enough movement to accommodate the stroke, as in U.S. Pat. No. 5,007,655 to Hanna, his FIG. 4, U.S. Pat. No. 6,916,032 to Wong, and U.S. Pat. No. 5,272,928, FIG. 4, to Young. In order for a system to operate at maximum efficiency, the rewind spring must be strong enough to support fast reciprocation of the mechanism, along with the capability to match a long power stroke.
Some of the designs show a system which appears to furnish a very small forward movement of the vehicle for each power stroke, as does U.S. Pat. No. 6,942,234, to Chait, resulting in an insufficient top speed and too many power absorbing reversals.
A considerable number of prior patents disclose drive ratio changing devices, all of which require two parallel and separate mechanisms to function, and the majority of them do not permit ratio shifting while under way. Many require somewhat complicated and machined parts, which may be too expensive, considering the end product in which they are employed.
U.S. Pat. No. 5,282,640, to Lindsey, discloses a scooter that is propelled by back-and-forth reciprocation of a single handlebar. It would appear that this will not be effective, as the operator is not able to spread his feet front-to-back on the platform in order to exert enough horizontal force on the handlebars. This is in contrast to the present invention, which uses vertical force to operate the mechanism, and the operator can easily apply his weight to the handlebars.
Several of the scooters in the prior art are steered by side-to-side tilting of the vehicle, including two by Chait, U.S. Pat. Nos. 6,708,997 and 6,942,234. A unique and complicated steering method is used in U.S. Pat. No. 5,690,346 to Keskitalo, and in U.S. Pat. No. 5,272,928, to Young. These steering methods are considered to be much less effective than the conventional handlebar method, which is used in the present invention.